Fluorescent nanocrystals encapsulated in an inorganic shell

Abstract

The present invention relates to a method of preparing hybrid organo/mineral nanoparticles comprising an organic fluorescent crystalline core encapsulated in an inorganic shell, and to nanoparticles that can be obtained by said method. The method of the present invention comprises the following steps: (i) a sol-gel mixture able to be obtained by a process comprising the addition, in at least one organic solvent, in the presence of water, of a fluorescent organic compound and at least one metal alkoxide is sprayed; (ii) the sprayed sol-gel mixture is dried, by evaporating the solvent and the water that are present in the sol-gel mixture. The nanoparticles of the present invention can be used for example as a tracer in medical imaging or as a chemical sensor.

The invention claimed is: 
     
       1. A process for preparing nanoparticles comprising a fluorescent organic nanocrystal core coated with an inorganic shell, said process comprising the following steps:
 (i) nebulizing a homogenous sol-gel mixture that is obtained via a process comprising the addition of at least one organic solvent, in the presence of water, of at least one fluorescent organic compound and of at least one metal alkoxide of formula (I) below:
   R 1   x M(OR 2 ) y    Formula (I)
 
 in which: 
 M is a metal chosen from the group comprising Si, Ti, Zr, Sn, B, Al and Y; 
 x is an integer ranging from 0 to 2; 
 y is an integer ranging from 1 to 6; 
 R 1  and R 2  independently represent an organic radical that is compatible with sol-gel chemistry; 
 
 (ii) drying the nebulized homogenous sol-gel mixture by evaporating off the solvent and the water present in the homogenous sol-gel mixture. 
 
     
     
       2. The process as claimed in  claim 1 , performed with at least one of the following conditions:
 (a) the fluorescent organic compound is chosen from the group comprising the polyaromatic family, the stilbene family, the naphthalimide family, the rhodamine family, the diarylmethane family, the perylene diimide family, boron dipyrromethene difluoride derivatives, and rare-earth metal complexes; 
 (b) the metal alkoxide is chosen from the group comprising tetramethoxysilane (TMOS, Si(OCH 3 ) 4 ), tetraethoxysilane (TEOS, Si(OC 2 H 5 ) 4 ), methyltrimethoxysilane (MTMOS, CH 3 Si(OCH 3 ) 3 ), ethyltriethoxysilane (ETEOS, C 2 H 5 Si(OC 2 H 5 ) 3 ), 1,2-bis(trimethoxysily)ethane (TMSE), 3-glycidoxypropyl)trimethoxysilane (GPTMS), or a mixture thereof; 
 (c) the solvent is chosen from the group comprising the alcohols R s —OH in which R s  is a C 1  to C 6  alkyl radical, the ketones R S1 —C(═O)—R s2 , the ethers R S1 —O—R S2 , in which R S1  and R S2  are independently C 1  to C 6  alkyl radicals, tetrahydrofuran, acetonitrile, dimethylformamide, toluene, dimethyl sufoxide, dioxane, acetone, acetic acid, formic acid, dichloromethane, chloroform, dichloroethane, ethyl acetate, diethyl ether or a mixture thereof. 
 
     
     
       3. The process as claimed in  claim 1 , in which the fluorescent organic compound is chosen from the group comprising rubrene, tetracene, cyano-methoxy-nitro-stilbene (CMONS), diethylamino-nitro-stilbene, rhodamine B, auramine O and europium, ytterbium, erbium and neodymium complexes. 
     
     
       4. The process as claimed in any one of  claims 1  to  3 , in which the drying step (ii) is performed with at least one of the following conditions:
 with temperature and pressure conditions allowing the evaporation of the solvent and the water present in the homogenous sol-gel mixture; 
 under a stream of dry gas; 
 in the presence of a material that can uptake the at least one solvent.